The present invention relates to gas turbine engines, and more particularly to fairing platforms for a fan section of gas turbine engines.
Gas turbine engines, such as turbofan engines for an aircraft, include a fan section, a compression section, a combustion section, and a turbine section. A primary flow path for working medium flow gases extends axially through the sections of the engine. A secondary flow path (bypass) for flow gases extends parallel to and radially outward of the primary flow path and passes through the fan section.
The fan section includes a rotor assembly and a stator assembly. The rotor assembly of the fan includes a fan hub and a plurality of outwardly extending airfoils. Each airfoil includes a blade portion, a root portion, and a fairing platform. The blade portion of the airfoil extends through the flow path and interacts with the gases passing therethrough to transfer energy between the rotor assembly and the gases. The fairing platform typically extends circumferentially from the rotor blade to an adjacent rotor blade and is disposed radially between the blade portion and the root portion. The stator assembly includes a fan case, which circumscribes the rotor assembly in close proximity to the tips of the blades.
During operation, the fan draws the gases (air) into the engine. The fan (driven by the turbine) raises the pressure of the air drawn along the secondary flow path, thus producing useful thrust. Improvements in fan performance depend in many cases on reducing fluid flow leakage at various points in the fan. One of these places is between adjacent fan blades at the inner radial portions thereof adjacent the fan hub. Typically, fairing platforms are utilized to seal this gap and to form the inner fan air flow path between the fan blades. Indeed, the gap must be sealed to prevent leakage recirculation from the blade trailing edge forward and up through the gap into the fan flow path.
Traditionally, fairing platforms were created from stock along with the fan blade. Rubber flap seals were then used to seal the gaps between adjacent fairing platforms. However, as fan blades are typically constructed of alloys, machining the fairing platform from stock is expensive and time consuming. Thus, alternative fairing platform designs have been developed. These alternatives typically use a fairing platform that is separate from the blade and hub. This alternative design is constructed of composite materials using expensive resin transfer molding techniques and utilizes an epoxy bulk seal. The fairing platform is typically fastened to the hub with lugs or pins. Such a retention configuration adds additional material and components to the fan section and can complicate assembly.